1. Field of the Invention
The present invention relates to a method of printing a thermal medium by aligning an image. More particularly, the present invention relates to a method of printing a thermal medium that is used in a thermal printer by aligning print starting positions of first and second surfaces of the thermal medium.
2. Description of the Related Art
A thermal printer can be classified into a printer using a medium that represents a predetermined color according to heat applied to a thermal medium or a printer using an ink ribbon that transfers a predetermined color onto a general medium according to heat applied to the ink ribbon. The latter one uses a driving device for operating the ink ribbon. Thus it has a fairly complex structure and a relatively high price. Also, since the ink ribbon should be replaced continually, a printing price per page may be high.
Referring to FIG. 1, a thermal medium 10 includes a base sheet 11 having first and second surfaces 10a and 10b on which ink layers of predetermined colors are formed, respectively. The ink layers are formed to have different colors from each other. For example, a yellow (Y) layer and a magenta (M) layer are sequentially stacked on the first surface 10a, and a cyan (C) layer is formed on the second surface 10b. It is desirable that the base sheet 11 is formed of a transparent material. Reflective layer 13 reflects light so that a color image can be seen on the first surface 10a. U.S. Published Patent Application No. 2003/0125206 discloses an example of the thermal medium 10.
The thermal printer uses a thermal printhead (TPH). The thermal printhead has heating elements which are disposed perpendicularly to a proceeding direction of the printing sheet.
FIG. 2 illustrates a structure of a general thermal printer.
Referring to FIG. 2, the thermal printer includes a feeding roller 2 that conveys the thermal medium 10, a platen 3 to support a surface of the medium 10, and a TPH 4 to form an image on the medium 10 that is disposed on the platen 3.
When the TPH is rotated for printing images on the second surface after printing images on the first surface, if the TPH is not aligned with the medium, the color printing operation may be improperly performed.
Therefore, a method of aligning a print starting position of the medium is required when the first and second surfaces of the medium are printed.
Accordingly, there is a need for an improved method of aligning a print starting position of the medium when the first and second surfaces of the medium are printed.